In cooperation with neighboring municipalities, Kumamoto City has maintained groundwater recharge levels and protected watershed forests. By protecting the natural systems and conserving Kumamoto's high-quality groundwater, the city can provide its citizens with high quality mineral water from the tap.
Source: The ICLEI Case Study series

Kumamoto City has carried out various initiatives to conserve its groundwater, including the adoption of the Declaration of the Groundwater Preservation City in 1976, and the installation of groundwater observation wells in 1986. As part of
these efforts, the city has conducted research on groundwater flows.